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  • Best way to enforce inter-table constraints inside database

    - by FerranB
    I looking for the best way to check for inter-table constraints an step forward of foreing keys. For instance, to check if a date child record value is between a range date on two parent rows columns. For instance: Parent table ID DATE_MIN DATE_MAX ----- ---------- ---------- 1 01/01/2009 01/03/2009 ... Child table PARENT_ID DATE ---------- ---------- 1 01/02/2009 1 01/12/2009 <--- HAVE TO FAIL! ... I see two approaches: Create materialized views on-commit as shown in this article (or other equivalent on other RDBMS). Use stored-procedures and triggers. Any other approach? Which is the best option? UPDATE: The motivation of this question is not about "putting the constraints on database or on application". I think this is a tired question and anyone does the way she loves. And, I'm sorry for detractors, I'm developing with constraints on database. From here, the question is "which is the best option to manage inter-table constraints on database?". I'm added "inside database" on the question title. UPDATE 2: Some one added the "oracle" tag. Of course materialized views are oracle-tools but I'm interested on any option regardless it's on oracle or others RDBMSs.

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  • If I'm using a 1d array to represent a square board, how can I take my index and check the sqaures a

    - by FrankTheTank
    If I have a 4x4 gameboard which I'm representing in my program as a 1d integer array of size 16. How can I get the indexs of the squares above, below, to the left and to the right any given index? So, for example: A = { 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 } Which represents this board 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Lets say I am currently on index #8 in the board (value = 7). How can I get the index for 4 (value = 3) , 5 (value = 6), 10 (value = 11) and realize that there is no right square because it is on the right hand edge of the board. I know I need to use some modulus math but I'm failing to come up with the right way to get the indexes for adjacent squares. I'm thinking something like... if ((i % 4) + 1 < 3) right = i + 1; if ((i % 4) - 1 > 0) left = i - 1; if ((i % 4) + 4 < 15) bottom = i + 4; if ((i % 4) - 4 > 0 ) top = i - 4; Does this seem like it is the right approach?

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  • Idiom vs. pattern

    - by Roger Pate
    In the context of programming, how do idioms differ from patterns? I use the terms interchangeably and normally follow the most popular way I've heard something called, or the way it was called most recently in the current conversation, e.g. "the copy-swap idiom" and "singleton pattern". The best difference I can come up with is code which is meant to be copied almost literally is more often called pattern while code meant to be taken less literally is more often called idiom, but such isn't even always true. This doesn't seem to be more than a stylistic or buzzword difference. Does that match your perception of how the terms are used? Is there a semantic difference?

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  • tfidf, am I understanding it right?

    - by alskndalsnd
    Hey everyone, I am interested in doing some document clustering, and right now I am considering using TF-IDF for this. If I am not wrong, TFIDF is particularly used for evaluating the relevance of a document given a query. If I do not have a particular query, how can I apply tfidf to clustering?

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  • Why are there so many Database Management Systems?

    - by mr.bio
    Why are there so many Database management systems? I am not an DB expert and I've never thought about using another Database other than mySQL. Programming languages offer different paradigms, so it makes sense to choose a specific language for your purpose. Question What are the factors in choosing a specific Database management system ?

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  • Naming convention for non-virtual and abstract methods

    - by eagle
    I frequently find myself creating classes which use this form (A): abstract class Animal { public void Walk() { // TODO: do something before walking // custom logic implemented by each subclass WalkInternal(); // TODO: do something after walking } protected abstract void WalkInternal(); } class Dog : Animal { protected override void WalkInternal() { // TODO: walk with 4 legs } } class Bird : Animal { protected override void WalkInternal() { // TODO: walk with 2 legs } } Rather than this form (B): abstract class Animal { public abstract void Walk(); } class Dog : Animal { public override void Walk() { // TODO: do something before walking // custom logic implemented by each subclass // TODO: walk with 4 legs // TODO: do something after walking } } class Bird : Animal { public override void Walk() { // TODO: do something before walking // custom logic implemented by each subclass // TODO: walk with 2 legs // TODO: do something after walking } } As you can see, the nice thing about form A is that every time you implement a subclass, you don't need to remember to include the initialization and finalization logic. This is much less error prone than form B. What's a standard convention for naming these methods? I like naming the public method Walk since then I can call Dog.Walk() which looks better than something like Dog.WalkExternal(). However, I don't like my solution of adding the suffix "Internal" for the protected method. I'm looking for a more standardized name. Btw, is there a name for this design pattern?

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  • Code Golf: Diamond Pattern

    - by LiraNuna
    The challenge The shortest code by character count to output a a pattern of diamonds according to the input. The input is composed of 3 positive numbers representing the size of the diamond and the size of the grid. A diamond is made from the ASCII characters / and \ with spaces. A diamond of size 1 is: /\ \/ The size of the grid consists from width and height of number of diamonds. Test cases Input: 1 6 2 Output: /\/\/\/\/\/\ \/\/\/\/\/\/ /\/\/\/\/\/\ \/\/\/\/\/\/ Input: 2 2 2 Output: /\ /\ / \/ \ \ /\ / \/ \/ /\ /\ / \/ \ \ /\ / \/ \/ Input 4 1 3 Output: /\ /\ /\ / \ / \ / \ / \ / \ / \ / \/ \/ \ \ /\ /\ / \ / \ / \ / \ / \ / \ / \/ \/ \/ Code count includes input/output (i.e full program).

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  • Should I use `!IsGood` or `IsGood == false`?

    - by chills42
    I keep seeing code that does checks like this if (IsGood == false) { DoSomething(); } or this if (IsGood == true) { DoSomething(); } I hate this syntax, and always use the following syntax. if (IsGood) { DoSomething(); } or if (!IsGood) { DoSomething(); } Is there any reason to use '== true' or '== false'? Is it a readability thing? Do people just not understand Boolean variables? Also, is there any performance difference between the two?

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  • What should every developer know about databases?

    - by Aaronaught
    Whether we like it or not, many if not most of us developers either regularly work with databases or may have to work with one someday. And considering the amount of misuse and abuse in the wild, and the volume of database-related questions that come up every day, it's fair to say that there are certain concepts that developers should know - even if they don't design or work with databases today. So: What are the important concepts that developers and other software professionals ought to know about databases? Guidelines for Responses: Keep your list short. One concept per answer is best. Be specific. "Data modelling" may be an important skill, but what does that mean precisely? Explain your rationale. Why is your concept important? Don't just say "use indexes." Don't fall into "best practices." Convince your audience to go learn more. Upvote answers you agree with. Read other people's answers first. One high-ranked answer is a more effective statement than two low-ranked ones. If you have more to add, either add a comment or reference the original. Don't downvote something just because it doesn't apply to you personally. We all work in different domains. The objective here is to provide direction for database novices to gain a well-founded, well-rounded understanding of database design and database-driven development, not to compete for the title of most-important.

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  • Algorithm to find the percentage of how much two texts are identical

    - by qster
    What algorithm would you suggest to identify how much from 0 to 1 (float) two texts are identical? Note that I don't mean similar (ie, they say the same thing but in a different way), I mean exact same words, but one of the two texts could have extra words or words slightly different or extra new lines and stuff like that. A good example of the algorithm I want is the one google uses to identify duplicate content in websites (X search results very similar to the ones shown have been omitted, click here to see them). The reason I need it is because my website has the ability for users to post comments; similar but different pages currently have their own comments, so many users ended up copy&pasting their comments on all the similar pages. Now I want to merge them (all similar pages will "share" the comments, and if you post it on page A it will appear on similar page B), and I would like to programatically erase all those copy&pasted comments from the same user. I have quite a few million comments but speed shouldn't be an issue since this is a one time thing that will run in the background. The programming language doesn't really matter (as long as it can interface to a MySQL database), but I was thinking of doing it in C++.

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  • Code Golf: Morse code

    - by LiraNuna
    The challenge The shortest code by character count, that will input a string using only alphabetical characters (upper and lower case), numbers, commas, periods and question mark, and returns a representation of the string in Morse code. The Morse code output should consist of a dash (-, ascii 0x2D) for a long beep (aka 'dah') and a dot (., ascii 0x2E) for short beep (aka 'dit'). Each letter should be separated by a space (' ', ascii 0x20), and each word should be separated by a forward slash (/, ascii 0x2F). Morse code table: Test cases: Input: Hello world Output: .... . .-.. .-.. --- / .-- --- .-. .-.. -.. Input: Hello, Stackoverflow. Output: .... . .-.. .-.. --- --..-- / ... - .- -.-. -.- --- ...- . .-. ..-. .-.. --- .-- .-.-.- Code count includes input/output (i.e full program).

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  • Are there any strongly typed scripting languages?

    - by George Edison
    I am wondering if there are any strongly typed scripting languages. Python, JavaScript, etc. are great languages, but they are (to a certain degree) loosely typed. I am just wondering if anyone knows of any strongly typed scripting languages. And by scripting, I mean a language whose interpreter can be embedded in a C++ application.

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  • What is "elegant" code?

    - by Breton
    I see a lot of lip service and talk about the most "elegant" way to do this or that. I think if you spend enough time programming you begin to obtain a sort of intuitive feel for what it is we call "elegance". But I'm curious. Even if we can look at a bit of code, and say instinctively "That's elegant", or "That's messy", I wonder if any of us really understands what that means. Is there a precise definition for this "elegance" we keep referring to? If there is, what is it? Now, what I mean by a precise definition, is a series of statements which can be used to derive questions about a peice of code, or a program as a whole, and determine objectively, or as objectively as possible, whether that code is "elegant" or not. May I assert, that perhaps no such definition exists, and it's all just personal preference. In this case, I ask you a slightly different question: Is there a better word for "elegance", or a better set of attributes to use for judging code quality that is perhaps more objective than merely appealing to individual intuition and taste? Perhaps code quality is a matter of taste, and the answer to both of my questions is "no". But I can't help but feel that we could be doing better than just expressing wishy washy feelings about our code quality. For example, user interface design is something that to a broad range of people looks for all the world like a field of study that oughtta be 100% subjective matter of taste. But this is shockingly and brutally not the case, and there are in fact many objective measures that can be applied to a user interface to determine its quality. A series of tests could be written to give a definitive and repeatable score to user interface quality. (See GOMS, for instance). Now, okay. is Elegance simply "code quality" or is it something more? Is it something that can be measured? Or is it a matter of taste? Does our profession have room for taste? Maybe I'm asking the wrong questions altogether. Help me out here. Bonus Round If there is such a thing as elegance in code, and that concept is useful, do you think that justifies classifying the field of programming as an "Art" capital A, or merely a "craft". Or is it just an engineering field populated by a bunch of wishful thinking humans? Consider this question in the light of your thoughts about the elegance question. Please note that there is a distinction between code which is considered "art" in itself, and code that was written merely in the service of creating an artful program. When I ask this question, I ask if the code itself justifies calling programming an art. Bounty Note I liked the answers to this question so much, I think I'd like to make a photographic essay book from it. Released as a free PDF, and published on some kind of on demand printing service of course, such as "zazz" or "tiggle" or "printley" or something . I'd like some more answers, please!

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  • Problem wit MDAC when trying to compile in VS2008 using x64 bit target platform

    - by grobartn
    I am trying to compile an 32 bit application. I am aware of problems with it but that is why its being compiled on 64 bit version. I am hanging at this problem. Application uses lots of sql stuff. In sqltypes.h file: (provided by MDAC) #ifdef _WIN64 typedef INT64 SQLLEN; typedef UINT64 SQLULEN; typedef UINT64 SQLSETPOSIROW; #else For some reason when its compiled on 32 bit platform it works great But when I try building it on 64 it goes berserk. Error 61 error C2146: syntax error : missing ';' before identifier 'SQLLEN' ..\external\microsoft sdk\include\sqltypes.h 50 It does not recognize INT64, UINT64. Is there something I need to enable so it will work under 64 build process? Missing some #include or #define? Any help would be great Thanks

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  • data structure algorithms for database searching

    - by Ygam
    I was used to the traditional way of doing database searching with the following using wildcards for term searches using where clause for specific data like addresses and names but at other times, I found these common methods to produce code that is so bloated, especially when it comes to complex searches. Are there algorithms out there that you use for complex database searching? I tried to look for some but had a hard time doing so. I stumbled accross the binary search but I can't find a use for it :(

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  • Code Golf: Banknote calculator

    - by paxdiablo
    This question was posted by a C beginner and it was an exercise to calculate, given a dollar value input by the user, the minimum number of bills (or banknotes, depending on your locale) needed to reach that dollar value. So, if the user entered 93, the output would be: $20 bills = 4 $10 bills = 1 $5 bills = 0 $1 bills = 3 Finally succumbing to the phenomenon (it's a slow day here), I thought this would be ripe for a game of Code Golf. For fairness, the input prompt needs to be (note the "_" at the end is a space): Enter a dollar amount:_ I think I've covered all the bases: no identical question, community wiki. I won't be offended if it gets shut down though - of course, I'll never be able to complain about these types of questions again, for fear of being labelled a hypocrite :-) Okay, let's see what you can come up with. Here's a sample run: Enter a dollar amount: 127 $20 bills = 6 $10 bills = 0 $5 bills = 1 $1 bills = 2

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  • Defend zero-based arrays

    - by DrJokepu
    A question asked here recently reminded me of a debate I had not long ago with a fellow programmer. Basically he argued that zero-based arrays should be replaced by one-based arrays since arrays being zero based is an implementation detail that originates from the way arrays and pointers and computer hardware work, but these sort of stuff should not be reflected in higher level languages. Now I am not really good at debating so I couldn't really offer any good reasons to stick with zero-based arrays other than they sort of feel like more appropriate. I am really interested in the opinions of other developers, so I sort of challenge you to come up with reasons to stick with zero-based arrays!

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  • What is the worst programming mistake you have made?

    - by George Edison
    Most of us are not perfect. (Well, except Jon Skeet) Have you made a terrible mistake that you would like to share? The idea is that we could all learn from our mistakes and by collecting them together here, we can avoid some common ones and discover some no-so-common ones we may have overlooked. Oh, and this question is CW, of course. Edit: This question is different than http://stackoverflow.com/questions/1928002/what-is-the-worst-programming-mistake-you-have-ever-seen because we are sharing our own mistakes. Edit again: And this one http://stackoverflow.com/questions/130965/what-is-the-worst-code-youve-ever-written is different too - it asks for code. My question does not have that restriction!

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  • Derivative of a Higher-Order Function

    - by Claudiu
    This is in the context of Automatic Differentiation - what would such a system do with a function like map, or filter - or even one of the SKI Combinators? Example: I have the following function: def func(x): return sum(map(lambda a: a**x, range(20))) What would its derivative be? What will an AD system yield as a result? (This function is well-defined on real-number inputs).

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  • Programming challenge: can you code a hello world program as a Palindrome?

    - by Assaf Lavie
    So the puzzle is to write a hello world program in your language of choice, where the program's source file as a string has to be a palindrome. To be clear, the output has to be exactly "Hello, World". Edit: Well, with comments it seems trivial (not that I thought of it myself of course [sigh].. hat tip to cobbal). So new rule: no comments. Edit: I feel kind of bad editing someone else's question to say this, but it will eliminate a lot of non-palindromes that keep popping up, and I'm tired of seeing the same simple mistake over and over. The following is NOT a palindrome: ()() The following IS a palindrome: ())( Brackets, parenthesis, and anything else that must match are a major barrier to palindrome-ing, yes, but that doesn't mean you can ignore them and post non-palindrome answers. Languages represented thus far: C, C++, Bash, elisp, C#, Perl, sh, Windows shell, Java, Common Lisp, Awk, Ruby, Brainfuck, Funge, Python, Machine Language, HQ9+, Assembly, TCL, J, php, Haskell, io, TeX, APL, Javascript, mIRC Script, Basic, Orc, Fortran, Unlambda, Pseudo-code, Befunge, CFML, Lua, INTERCAL, VBScript, HTML, sed, PostScript, GolfScript, REBOL, SQL

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